Post on 30-Sep-2020
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Supporting Information for:
Rh-Catalyzed Oxidative C-H Activation/Annulation: Converting Anilines to
Indoles with Molecular Oxygen as Sole Oxidant
Guoying Zhang, Hui Yu, Guiping Qin, Hanmin Huang*
State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of
Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, P. R. China
E-mail: hmhuang@licp.cas.cn
CONTENTS
1 General experimental details and materials
2 Optimization of the reaction conditions
3 General procedure for the C-H activation/annulation
4 Experimental characterization data for products
5 Mechanistic studies
6 References
7 Copies for 1H NMR and
13C NMR of the indole products
Electronic Supplementary Material (ESI) for ChemComm.This journal is © The Royal Society of Chemistry 2014
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1. General experiment details and materials
Experimental: All non-aqueous reactions and manipulations were using standard
Schlenk techniques. All solvents were purchased from Alfa Aesar, and before use were
dried and degassed by standard methods and stored under argon atmosphere. All
reactions were monitored by TLC with silica gel-coated plates. NMR spectra were
recorded on BRUKER Avence III 400 MHz spectrometers. Chemical shifts were
reported in parts per million (ppm) down field from TMS with the solvent resonance as
the internal standard. Coupling constants (J) were reported in Hz and refered to
apparent peak multiplications. High resolution mass spectra (HRMS) were recorded on
Bruker MicroTOF-QII mass instrument (ESI) or Waters GCT Premier mass
spectrometer (EI). Anilines used here are known compounds. 1,2-diphenylethyne and
prop-1-ynylbenzene were purchased from Alfa Aesar. The other alkynes used here are
known compounds and synthesized according to the reported methods.1
Cp*Rh(H2O)3(OTf)2, Cp*Rh(H2O)(OAc)2 and Cp*Rh(CH3CN)3(SbF6)2,
[{RhCp*Cl2}2], used here are known compounds and synthesized according to the
reported methods.2
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2. Optimization of the reaction conditions
Diphenylethyne 2a (71.3 mg, 0.4 mmol), [Rh] catalyst (0.02 mmol, 5 mol%),
aniline 1a (55.0 µL, 0.6 mmol), solvent (2.0 mL) and Ac2O (57.0 µL, 0.6 mmol) were
added to a 25 mL flame-dried Young-type tube. The mixture was degassed by the
freeze-thaw method and supplied with 1 atm of oxygen, and then stirred at design
temperature for 24 hours. After cooling to room temperature, NaOH (48.0 mg, 1.2
mmol) and CH3OH (2.0 mL) were added to the reaction mixture, and then stirred at
room temperature for another one hour. After evaporation of the solvents under
reduced pressure, the residue was directly loaded onto a silica gel column (petroleum
ether/ethyl acetate = 100/1) to afford the desired product 3aa as a white solid.
Table 1. Optimization of the reaction conditionsa
Entry [Rh] (5 mol%) Additive T/ oC Solvent Yield (%)
b
1 Cp*Rh(H2O)3(OTf)2 Ac2O 40 t-AmOH 70
2 Cp*Rh(H2O)3(OTf)2 Ac2O 40 t-BuOH 18
3 Cp*Rh(H2O)3(OTf)2 Ac2O 40 CH3OH <5
4 Cp*Rh(H2O)3(OTf)2 Ac2O 40 DMF <5
5 Cp*Rh(H2O)3(OTf)2 Ac2O 40 CH3C(O)CH3 49
6 Cp*Rh(CH3CN)3(SbF6)2 Ac2O 40 t-AmOH <5
7 [{RhCp*Cl2}2] Ac2O 40 t-AmOH 0
8 Cp*Rh(H2O)(OAc)2 Ac2O 40 t-AmOH <5
9 Cp*Rh(H2O)3(OTf)2 Ac2O 60 t-AmOH 80
10 Cp*Rh(H2O)3(OTf)2 Ac2O 80 t-AmOH 79
11 Cp*Rh(H2O)3(OTf)2 Ac2O 100 t-AmOH 84
12 Cp*Rh(H2O)3(OTf)2 Ac2O 120 t-AmOH 81
13 Cp*Rh(H2O)3(OTf)2 Ac2O rt t-AmOH 44
14 Cp*Rh(H2O)3(OTf)2 Ac2O 100 t-AmOH <5c
15 Cp*Rh(H2O)3(OTf)2 (CF3CO)2O 100 t-AmOH 0
16 Cp*Rh(H2O)3(OTf)2 (CF3SO2)2O 100 t-AmOH 0
17 Cp*Rh(H2O)3(OTf)2 HOAc 100 t-AmOH 0
18 Cp*Rh(H2O)3(OTf)2 -- 100 t-AmOH 0
19 -- Ac2O 100 t-AmOH 0
a General conditions: 1a (55.0 µL, 0.6 mmol), 2a (71.3 mg, 0.4 mmol), [Rh] catalyst (0.02 mmol,
5mol %), additive (0.6 mmol), solvents (2.0 mL), oxygen (1 atm), for 24 h, unless otherwise noted. b
Isolated yield. c Under argon.
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3. General procedure for the C-H activation/annulation
Alkynes 2 (0.4 mmol), Cp*Rh(H2O)3(OTf)2 (11.8 mg, 0.02 mmol, 5 mol%), anilines
1 (0.6 mmol), t-AmOH (2.0 mL) and Ac2O (57.0 µL, 0.6 mmol) were added to a 25
mL flame-dried Young-type tube. The mixture was degassed by the freeze-thaw
method and supplied with 1 atm of oxygen, and then stirred at 100 oC or 40
oC for 24
hours. After cooling to room temperature, NaOH (48.0 mg, 1.2 mmol) and CH3OH
(2.0 mL) were added to the reaction mixture, and then stirred at room temperature for
another one hour. After evaporation of the solvents under reduced pressure, the residue
was directly loaded onto a silica gel column (petroleum ether/ethyl acetate = 100/1 –
5:1) to afford the desired products 3.
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4. Experimental characterization data for products of 3.
2,3-Diphenyl-1H-indole (3aa):3
The title compound was prepared according to the general procedure
as a white solid, 90.3 mg, 84% yield. 1H NMR (400 MHz, CDCl3) δ
7.13-7.17 (m, 1H), 7.21-7.45 (m, 12H), 7.67 (d, J = 7.68, 1H), 8.18
(br, 1H); 13
C NMR (100 MHz, CDCl3) δ 110.9, 115.0, 119.7, 120.4, 122.7, 126.2,
127.7, 128.1, 128.5, 128.7, 128.7, 130.1, 132.7, 134.0, 135.0, 135.9. HRMS (EI) calcd.
for C20H15N [M]: 269.1204, found: 269.1205.
5-Methyl-2,3-diphenyl-1H-indole (3ba):4
The title compound was prepared according to the general
procedure as a white solid, 105.6 mg, 93% yield. 1H NMR (400
MHz, CDCl3) δ 2.44 (s, 3H), 7.06-7.08 (m, 1H), 7.25-7.33 (m, 5H),
7.36-7.45 (m, 7H), 8.13 (br, 1H); 13
C NMR (100 MHz, CDCl3) δ 21.6, 110.6, 114.7,
119.3, 124.3, 126.2, 127.6, 128.1, 128.5, 128.7, 129.1, 129.8, 130.2, 132.9, 134.2,
134.2, 135.2; HRMS (ESI) calcd. for C21H18N [M+H]: 284.1434, found: 284.1436.
6-Methyl-2,3-diphenyl-1H-indole (3ca):5
The title compound was prepared according to the general
procedure as a white solid, 80.1 mg, 71% yield. 1H NMR (400
MHz, CDCl3) δ 2.34 (s, 3H), 6.86-6.88 (m, 1H), 7.03 (s, 1H),
7.13-7.19 (m, 4H), 7.23-7.27 (m, 4H), 7.31-7.33 (m, 2H), 7.45 (d, J = 8.14, 1H), 7.86
(br, 1H); 13
C NMR (100 MHz, CDCl3) δ 21.7, 110.8, 114.8, 119.3, 122.2, 126.1, 126.6,
127.4, 128.0, 128.5, 128.6, 130.1, 132.6, 132.8, 133.4, 135.2, 136.3; HRMS (ESI)
calcd. for C21H18N [M+H]: 284.1434, found: 284.1435.
5-tert-butyl-2,3-diphenyl-1H-indole (3da):
The title compound was prepared according to the general
procedure as a white solid, 120.1 mg, 92% yield. 1H NMR (400
MHz, CDCl3) δ 1.36 (s, 9H), 7.23-7.45 (m, 12H), 7.67 (s, 1H),
8.06 (br, 1H); 13
C NMR (100 MHz, CDCl3) δ 32.0, 34.8, 110.5, 115.2, 115.4, 121.2,
126.2, 127.6, 128.3, 128.5, 128.7, 128.7, 130.3, 133.0, 134.2, 134.5, 135.4, 143.6;
HRMS (ESI) calcd. for C24H23NNa [M+Na]: 348.1710, found: 348.1723.
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6-tert-butyl-2,3-diphenyl-1H-indole (3ea):
The title compound was prepared according to the general
procedure as a white solid, 110.4 mg, 84% yield. 1H NMR
(400 MHz, CDCl3) δ 1.40 (s, 9H), 7.22-7.44 (m, 12H), 7.60 (d,
J = 8.4 Hz, 1H), 8.13 (br, 1H); 13
C NMR (100 MHz, CDCl3) δ 31.8, 34.9, 107.2, 114.9,
118.8, 119.2, 126.1, 126.5, 127.5, 128.1, 128.5, 128.7, 130.1, 133.0, 133.9, 135.3,
136.1, 146.4; HRMS (EI) calcd. for C24H23N [M]: 325.1830, found: 325.1833.
5-Methoxy-2,3-diphenyl-1H-indole (3fa):5
The title compound was prepared according to the general
procedure as a white solid, 107.4 mg, 90% yield. 1H NMR
(400 MHz, CDCl3) δ 3.82 (s, 3H), 6.89 (dd, J1 = 8.8 Hz, J2 =
2.5 Hz, 1H), 7.12 (d, J = 2.4 Hz, 1H), 7.25-7.33 (m, 5H), 7.36-7.44 (m, 6H), 8.12 (b,
1H); 13
C NMR (100 MHz, CDCl3) δ 55.9, 101.3, 111.7, 113.0, 115.0, 126.2, 127.6,
128.1, 128.6, 128.7, 129.2, 130.1, 131.1, 132.8, 135.0, 135.2, 154.8; HRMS (ESI)
calcd. for C21H18NO [M+H]: 300.1383 found: 300.1384.
4,6-Dimethoxy-2,3-diphenyl-1H-indole (3ga):
The title compound was prepared according to the general
procedure as a white solid, 80.2 mg, 61% yield. 1H NMR (400
MHz, DMSO-d6) δ 3.60 (s, 3H), 3.80 (s, 3H), 6.17 (d, J = 1.92
Hz, 1H), 6.56 (d, J = 1.92 Hz, 1H), 7.19-7.29 (m, 10H), 11.36
(br, 1H); 13
C NMR (100 MHz, DMSO-d6) δ 54.9, 55.2, 86.8, 91.8, 112.2, 113.5, 125.7,
126.6, 127.2, 127.7, 128.2, 128.7, 131.1, 131.3, 131.6, 132.8, 136.4, 137.6,154.4, 156.9;
HRMS (ESI) calcd. for C22H20NO2 [M+H]: 330.1489, found: 330.1491.
5,6-Dimethoxy-2,3-diphenyl-1H-indole (3ha):6
The title compound was prepared according to the general
procedure as a white solid, 100.7 mg, 76% yield. 1H NMR
(400 MHz, CDCl3) δ 3.89 (s, 3H), 3.94 (s, 3H), 6.94 (s, 1H),
7.09 (s, 1H), 7.28-7.44 (m, 10H), 8.10 (br, 1H); 13
C NMR (100
MHz, DMSO-d6) δ 55.7, 55.8, 94.9, 100.7, 113.3, 120.7, 125.9, 126.9, 127.7, 128.4,
128.7, 129.6, 130.6, 132.3, 132.8, 135.6, 145.1, 147.1. HRMS (EI) calcd. for
C22H19NO2 [M]: 329.1416, found: 329.1418.
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2,3-Diphenyl-5-(trifluoromethoxy)-1H-indole (3ia):
The title compound was prepared according to the general
procedure as a white solid, 110.0 mg, 78% yield. 1H NMR
(400 MHz, CDCl3) δ 6.98-7.01 (m, 1H), 7.17-7.29 (m, 11H),
7.42 (s, 1H), 8.13 (br, 1H); 13
C NMR (100 MHz, CDCl3) δ
110.5, 111.2, 114.3, 115.5, 116.0 (q, J = 254 Hz), 125.6, 127.1, 127.1, 127.5, 127.7,
127.7, 128.0, 128.9, 131.0, 133.1, 133.2, 135.0, 142.6, 142.6; 19
F NMR (376 MHz,
CDCl3) δ -57.88. HRMS (EI) calcd. for C21H14F3NO [M]: 353.1027, found: 353.1028.
5-Fluoro-2,3-diphenyl-1H-indole (3ja):4
The title compound was prepared according to the general
procedure as a white solid, 87.3 mg, 76% yield. 1H NMR (400
MHz, CDCl3) δ 6.93-6.98 (m, 1H), 7.25-7.39 (m, 12H), 8.14 (br,
1H); 13
C NMR (100 MHz, CDCl3) δ 104.5 (d, J = 24 Hz), 110.9 (d,
J = 27 Hz), 111.6 (d, J = 10 Hz), 115.2 (d, J = 5 Hz), 126.5, 128.0, 128.2, 128.7, 128.8,
129.2 (d, J = 10 Hz), 130.0, 132.4 (d, J = 4 Hz), 134.7, 135.9, 157.4 (d, J = 34 Hz); 19
F
NMR (376 MHz, CDCl3) δ -123.45. HRMS (EI) calcd. for C20H14FN [M]: 287.1110,
found: 287.1098.
5-Chloro-2,3-diphenyl-1H-indole (3ka):4
The title compound was prepared according to the general
procedure as a white solid, 109.7 mg, 90% yield. 1H NMR (400
MHz, CDCl3) δ 7.16 (dd, J1 = 8.6 Hz, J2 = 2.04 Hz, 1H),
7.27-7.34 (m, 5H), 7.35-7.41 (m, 6H), 7.62-7.63 (m, 1H), 8.21 (br, 1H); 13
C NMR (100
MHz, CDCl3) δ 111.9, 114.8, 119.2, 123.0, 126.2, 126.6, 128.1, 128.1, 128.7, 128.8,
129.9, 130.0, 132.2, 134.2, 134.4, 135.4. HRMS (EI) calcd. for C20H14ClN [M]:
303.0815, found: 303.0813.
4-Chloro-2,3-diphenyl-1H-indole (3la) and
6-Chloro-2,3-diphenyl-1H-indole (3la’) (1.08:1, Determined by NMR):4
The title compound was prepared
according to the general procedure as a
white solid, 59.2 mg, 49% yield. 1H NMR
(400 MHz, CDCl3) δ 7.09 (d, J = 1.88 Hz,
0.48H), 7.11 (d, J = 1.88 Hz, 0.52H), 7.27-7.41 (m, 11H), 7.54 (s, 0.51H), 7.57 (s,
0.49H), 8.19 (br, 0.95H); 13
C NMR (100 MHz, CDCl3) δ 110.8, 115.1, 120.6, 121.2,
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126.5, 127.4, 128.0, 128.1, 128.4, 128.7, 128.8, 130.1, 132.2, 134.5, 134.6, 136.2;
HRMS (EI) calcd. for C20H14ClN [M]: 303.0815, found: 303.0813.
5-Bromo-2,3-diphenyl-1H-indole (3ma):5
The title compound was prepared according to the general
procedure as a white solid, 125.9 mg, 90% yield. 1H NMR (400
MHz, CDCl3) δ 7.24-7.33 (m, 6H), 7.38-7.41 (m, 6H), 7.77 (t, J =
0.76 Hz, 1H), 8.24 (br, 1H); 13
C NMR (100 MHz, CDCl3) δ 112.3,
113.7, 114.7, 122.2, 125.5, 126.6, 128.1, 128.1, 128.7, 128.8, 130.1, 130.6, 132.1,
134.3, 134.5, 135.2. HRMS (EI) calcd. for C20H14BrN [M]: 347.0310, found:
347.0308.
2,3-Diphenyl-1H-indole-5-carbonitrile (3na):7
The title compound was prepared according to the general
procedure as a white solid, 36.0 mg, 31% yield. 1H NMR (400
MHz, DMSO-d6) δ 7.33-7.49 (m, 10H), 7.52-7.55 (m, 1H), 7.61
(d, J = 8.4 Hz, 1H), 7.90 (m, 1H), 12.21 (br, 1H); 13
C NMR (100 MHz, DMSO-d6) δ
101.8, 112.8, 113.8, 120.5, 124.1, 124.7, 126.7, 127.7, 128.2, 128.3, 128.6, 128.8,
129.7, 131.4, 133.8, 136.6, 137.8; HRMS (ESI) calcd. for C21H15N2 [M+H]: 295.1230,
found: 295.1233.
Figure S1. ORTEP drawing of product 3ma
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Methyl 2,3-diphenyl-1H-indole-5-carboxylate (3oa):7
The title compound was prepared according to the general
procedure as a white solid, 79.1 mg, 60% yield. 1H NMR
(400 MHz, DMSO-d6) δ 3.83 (s, 3H), 7.33-7.50 (m, 10H),
7.54 (d, J = 8.52, 1H), 7.81-7.84 (m, 1H), 8.15 (d, J = 1.36 Hz, 1H), 12.03 (br); 13
C
NMR (100 MHz, DMSO-d6) δ 51.7, 111.5, 114.5, 121.1, 121.1, 123.0,126.6, 127.7,
128.0, 128.2, 128.6, 128.8, 129.8, 131.8, 134.5, 135.8, 138.6, 167.1; HRMS (ESI)
calcd. for C22H18NO2 [M+H]: 328.1332, found: 328.1344.
2,3-Diphenyl-1H-benzo[g]indole (3pa):
The title compound was prepared according to the general
procedure as a white solid, 78.6 mg, 62% yield. 1H NMR (400
MHz, CDCl3) δ 7.28-7.55 (m, 13H), 7.72 (d, J = 8.68, 1H), 7.91
(d, J = 8.04, 1H), 8.02 (d, J = 8.16, 1H), 8.87 (br, 1H); 13
C NMR (100 MHz, CDCl3) δ
116.9, 119.4, 119.5, 121.3, 121.5, 124.2, 124.6, 125.7, 126.4, 127.5, 128.1, 128.6,
128.8, 129.0, 130.3, 130.8, 132.5, 132.8, 135.0; HRMS (EI) calcd. for C24H17N [M]:
319.1361, found: 319.1365.
2,3-Di-p-tolyl-1H-indole (3ab):5
The title compound was prepared according to the general
procedure as a white solid, 96.0 mg, 81% yield. 1H NMR (400
MHz, CDCl3) δ 2.23 (s, 3H), 2.28 (s, 3H), 6.99-7.13 (m, 6H),
7.18-7.26 (m, 5H), 7.56 (d, J = 7.96, 1H), 7.95 (br, 1H); 13
C
NMR (100 MHz, CDCl3) δ 21.4, 110.9, 114.6, 119.7, 120.4,
122.5, 128.1, 129.0, 129.4, 129.5, 130.0, 130.1, 132.2, 134.1, 135.8, 135.9, 137.6;
HRMS (ESI) calcd. for C22H20N [M+H]: 298.1590, found: 298.1595.
2,3-Bis(4-methoxyphenyl)-1H-indole (3ac):5
The title compound was prepared according to the general
procedure as a white solid, 111.8 mg, 85% yield. 1H NMR
(400 MHz, DMSO-d6) δ 3.77 (s, 3H), 3.79 (s, 3H),
6.93-7.04 (m, 5H), 7.11-7.15 (m, 1H), 7.25-7.28 (m, 2H),
7.39-7.44 (m, 4H), 11.39 (br, 1H); 13
C NMR (100 MHz,
CDCl3) δ 55.2, 55.3, 110.7, 113.8, 114.0, 114.2, 119.5, 120.2, 122.3, 125.3, 127.6,
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129.0, 129.3, 131.2, 133.7, 135.7, 158.7, 159.1; HRMS (ESI) calcd. for C22H20NO2
[M+H]: 330.1489, found: 330.1487.
2,3-Bis(4-fluorophenyl)-1H-indole (3ad):5
The title compound was prepared according to the general
procedure as a white solid, 93.0 mg, 76% yield. 1H NMR (400
MHz, CDCl3) δ 6.98-7.08 (m, 4H), 7.13-7.17 (m, 1H),
7.21-7.26 (m, 1H), 7.31-7.39 (m, 5H), 7.60 (d, J = 8.00, 1H),
8.12 (br, 1H); 13
C NMR (100 MHz, CDCl3) δ 111.0, 114.0,
115.5, 115.7 (d, J = 7 Hz), 116.0, 119.5, 120.7, 122.9, 128.6, 129.9, 130.0 (d, J = 8 Hz),
131.5 (d, J = 8 Hz), 133.2, 135.8, 160.4, 161.2 (d, J = 246 Hz), 162.9 (d, J = 244 Hz);
19F NMR (376 MHz, CDCl3) δ -116.2, -113.3; HRMS (EI) calcd. for C20H13F2N [M]:
305.1013, found: 305.1008.
2,3-Bis(4-bromophenyl)-1H-indole (3ae):5
The title compound was prepared according to the general
procedure as a white solid, 128.4 mg, 75% yield. 1H NMR
(400 MHz, CDCl3) δ 7.16 (t, J = 7.84, 1H), 7.24-7.29 (m, 5H),
7.40-7.51 (m, 5H), 7.61 (d, J = 7.96 Hz, 1H), 8.18 (br, 1H);
13C NMR (100 MHz, CDCl3) δ 111.1, 114.3, 119.5, 120.4,
120.9, 122.1, 123.3, 128.4, 129.7, 131.3, 131.7, 131.9, 132.1, 133.1, 133.7,
136.0.HRMS (EI) calcd. for C20H13Br2N [M]: 424.9415, found: 424.9426.
2-Phenyl-3-p-tolyl-1H-indole (3af) and
3-Phenyl-2-p-tolyl-1H-indole (3af’) (1.14:1, Determined by NMR):8
The title compound was prepared
according to the general procedure
as a white solid, 90.0 mg, 79% yield.
1H NMR (400 MHz, CDCl3) δ 2.31
(s, 1.36H), 2.36 (s, 1.64H),
7.07-7.44 (m, 12H), 7.65 (d, J =
7.92 Hz, 1H), 8.08 (br, 1H); 13
C NMR (100 MHz, CDCl3) δ 21.3, 110.8, 119.6, 119.8,
120.4, 122.5, 122.7, 126.2, 127.6, 128.0, 128.1, 128.5, 128.7, 128.8, 129.3, 129.4,
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130.0, 130.2, 132.0, 132.8, 134.2, 135.8, 135.9, 137.6; HRMS (ESI) calcd. for C21H18N
[M+H]: 284.1434, found: 284.1436.
2-(4-Bromophenyl)-3-phenyl-1H-indole (3ag) and
3-(4-Bromophenyl)-2-phenyl-1H-indole (3ag’) (1:1 Determined by NMR):7
The title compound was prepared
according to the general procedure as
a white solid, 86.6 mg, 62% yield.
1H NMR (400 MHz, CDCl3) δ
7.13-7.18 (m, 1H), 7.23-7.50 (m,
11H), 7.63-7.67 (m, 1H), 8.17 (br, 0.48H), 8.24 (br, 0.45H); 13
C NMR (100 MHz,
CDCl3) δ 111.0, 111.0, 113.8, 115.7, 119.4, 119.8, 120.2, 120.6, 120.7, 121.8, 122.9,
123.1, 126.5, 128.0, 128.2, 128.4, 128.7, 128.7, 128.9, 129.6, 130.1, 131.6, 131.7,
131.9, 132.4, 132.8, 134.1, 134.4, 134.7, 135.9, 136.0; HRMS (ESI) calcd. for
C20H18N2Br [M+NH4]: 365.0648, found: 365.0634.
2-(4-Bromophenyl)-3-phenyl-1H-indole (3ah):
The title compound was prepared according to the general
procedure as a white solid, 124.0 mg, 77% yield. 1H NMR
(400 MHz, CDCl3) δ 7.08-7.12 (m, 1H), 7.20-7.38 (m, 7H),
7.58 (d, J = 7.96 Hz, 1H), 7.66 (s, 1H), 7.72 (s, 2H), 8.21 (br,
1H); 13
C NMR (100 MHz, CDCl3) δ 111.2, 117.9, 120.3,
120.7 (heptet, J = 4 Hz), 121.1, 121.7 (q, J = 271 Hz), 124.0, 127.3, 127.7, 128.6,
129.0, 130.0, 130.5, 131.5 (q, J = 33 Hz), 133.7, 134.8, 136.4; 19
F NMR (376 MHz,
CDCl3) δ -63.2; HRMS (EI) calcd. for C22H13F6N [M]: 405.0952, found: 405.0945.
3-Methyl-2-phenyl-1H-indole (3ai):8
The title compound was prepared according to the general
procedure as a white solid, 43.0 mg, 52% yield. 1H NMR (400
MHz, DMSO-d6) δ 2.43 (s, 3H), 7.01-7.05 (m, 1H), 7.10-7.14 (m,
1H), 7.35-7.39 (m, 2H), 7.50-7.55 (m, 3H), 7.68-7.70 (m, 2H), 11.17 (br, 1H); 13
C
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NMR (100 MHz, DMSO-d6) δ 9.8, 106.7, 111.0, 118.4, 118.5, 121.5, 126.9, 127.5,
128.7, 129.4, 133.1, 133.7, 135.9; HRMS (ESI) calcd. for C15H14N [M+H]: 208.1121,
found: 208.1125.
3-Benzyl-2-phenyl-1H-indole (3aj) and
2-benzyl-3-phenyl-1H-indole (3aj’) (12:1 Determined by NMR):8
The title compound was prepared according to
the general procedure as a white solid, 57.2 mg,
50% yield. 1H NMR (400 MHz, DMSO-d6) δ
4.19 (s, 0.15H), 4.24 (s, 1.85H), 6.94-6.98 (m,
0.92H), 7.01-7.04 (m, 0.09H), 7.09-7.18 (m, 3.84H), 7.22-7.27 (m, 1.91H), 7.29-7.31
(m, 0.17H), 7.35-7.41 (m, 2.83H), 7.46-7.50 (m, 2.07H), 7.53-7.55 (m, 0.09H),
7.60-7.62 (m, 1.93H), 7.66-8.24 (m, 0.28H), 11.22 (br, 0.07H), 11.33 (br, 0.90); 13
C
NMR (100 MHz, DMSO-d6) δ 29.9, 109.7, 111.2, 118.7, 118.8, 121.6, 125.7, 127.4,
127.5, 127.9, 128.3, 128.6, 128.7, 128.8, 132.7, 134.9, 136.1, 141.5; HRMS (ESI)
calcd. for C21H18N [M+H]: 284.1428, found: 284.1434.
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5. Mechanistic studies
5.1 Rh/O2 catalytic system catalyzed aerobic C-H activation
Following our general procedure: 1,2-diphenylethyne 2a (71.3 mg, 0.4 mmol),
Cp*Rh(H2O)3(OTf)2 (11.8 mg, 0.02 mmol, 5 mol%), acetanilide (81.1mg, 0.6 mmol),
t-AmOH (2.0 mL) and AcOH (35 µL, 0.6 mmol) were added to a 25 mL flame-dried
Young-type tube. The mixture was degassed by the freeze-thaw method and supplied
with 1 atm of oxygen, and then stirred at 100 oC for 24 hours. After cooling to room
temperature, NaOH (48.0 mg, 1.2 mmol) and CH3OH (2.0 mL) were added into the
reaction mixture, and then stirred at room temperature for another one hour. After
evaporation of the solvents under reduced pressure, the residue was directly loaded
onto a silica gel column (petroleum ether/ethyl acetate = 100/1) to afford the desired
product 3aa in 85% yield (91.2 mg).
5.2 Substrate Competition Experiments
Following our general procedure: 1,2-diphenylethyne 2a (71.3 mg, 0.4 mmol),
Cp*Rh(H2O)3(OTf)2 (11.8 mg, 0.02 mmol, 5 mol%), p-toluidine 1b, (32.2mg, 0.3
mmol), 4-chloroaniline 1k (38.3 mg, 0.3 mmol), t-AmOH (2.0 mL) and Ac2O (57.0 µL,
0.6 mmol) were added to a 25 mL flame-dried Young-type tube. The mixture was
degassed by the freeze-thaw method and supplied with 1 atm of oxygen, and then
stirred at 100 oC for two hours. After cooling to room temperature, NaOH (48.0 mg,
1.2 mmol) and CH3OH (2.0 mL) were added into the reaction mixture, and then stirred
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at room temperature for another one hour. After evaporation of the solvents under
reduced pressure, the residue was directly loaded onto a silica gel column (petroleum
ether/ethyl acetate = 100/1) to afford the desired products 3ba (24.5% yield) and 3ka
(11.1% yield), respectively.
5.3 Synthesis of aniline (D5-1a’):9
Synthesis of D5-nitrobenzene:
Concentrated nitric acid (12.0 mL) and concentrated sulfuric acid (13.6 mL) were
mixed together in a 250 mL round-bottom flask held in 30-50 oC. Benzene-d6 (10.0 mL,
112 mmol) was added drop-wise at 80 oC and the mixture was allowed to stir at 60
oC
for an additional 45 minutes. Then the reaction mixture was poured into ice-water (100
mL) and extracted with DCM (3×50 mL). The combined organic layer was washed
with ice water (2×50 mL), sat. aq. NaHCO3 solution (2×50 mL), brine (2×40 mL), and
dried with anhydrous Na2SO4 for 24 hours. After distilling, faint yellow oil of
D5-nitrobenzene was obtained in 81 % yield, (11.7 g).
Synthesis of D5-aniline (D5-1a’):
D5-nitrobenzene (2.55 g), Pd/C (200 mg), MeOH (5 mL) were added to a teflon tube
which was placed in an autoclave. Then the autoclave was purged and charged with H2
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at 3 atm. The reaction mixture was stirred at room temperature for 16 hours, and then
H2 was carefully released. After evaporation of the solvents under reduced pressure,
the residue was directly loaded onto a silica gel column (petroleum ether/ethyl acetate
= 100/1) to afford the colorless oil desired product D5-aniline in 92 % yield (1.8 g).
5.4 Experimental detail for determination of the intramolecular KIE
Following our general procedure: 1,2-diphenylethyne (71.3 mg, 0.4 mmol),
Cp*Rh(H2O)3(OTf)2 (11.8 mg, 0.02 mmol, 5 mol%), D5-aniline (29.4 mg, 0.3 mmol),
aniline (27.5 mg, 0.3 mmol), t-AmOH (2.0 mL) and Ac2O (57.0 µL, 0.6 mmol) were
added to a 25 mL flame-dried Young-type tube. The mixture was degassed by the
freeze-thaw method and supplied with 1 atm of O2, and then stirred at 100 oC for two
hours. After cooling to room temperature, NaOH (48.0 mg, 1.2 mmol) and CH3OH
(2.0 mL) were added into the reaction mixture, and then stirred at room temperature for
another one hour. After evaporation of the solvents under reduced pressure, the residue
was directly loaded onto a silica gel column (petroleum ether/ethyl acetate = 100/1) to
afford the desired products 3aa (23.1% yield) and 3aa’ (6.6 % yield), respectively.
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6. References
1 P. Chuentragool, K. Vongnam, P. Rashatasakhon, M. Sukwattanasinitt and S. Wacharasindhu,
Tetrahedron., 2011, 67, 8177.
2 M. S. Eisen, A. Haskel, H. Chen, M. M. Olmstead, D. P. Smith, M. F. Maestre and R. H. Fish,
Organometallics., 1995, 14, 2806.
3 M. Shen, G. Li, B. Z. Lu, A. Hossain, F. Roschangar, V. Farina and C. H. Senanayake, Org. Lett.,
2004, 6, 4129.
4 C. Wang, H. Sun, Y. Fang and Y. Huang, Angew. Chem. Int. Ed., 2013, 52, 5795
5 X. Chen, X. Li, N. Wang, J. Jin, P. Lu and Y. Wang, Eur. J. Org. Chem., 2012, 4380.
6 J.-D. Charrier, C. Landreau, D. Deniaud, F. Reliquet, A. Reliquet and J. C. Meslin, Tetrahedron,
2001, 57, 4195.
7 B. Z. Lu, W. Zhao, H.-X. Wei, M. Dufour, V. Farina and C. H. Senanayake, Org. Lett., 2006, 8,
3271.
8 X. Fan and Y. Zhang, Tetrahedron 2003, 59, 1917.
9 D. R. Stuart, M. Bertrand-Laperle, K. M. N. Burgess and K. Fagnou, J. Am. Chem. Soc., 2008,
130, 16474.
7. Copies for 1H NMR and
13C NMR of the indole products
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